ELLSWORTH, Maine — Each of the three towns attempting to leave Regional School Unit 24 has passed a huge milestone in the withdrawal process: They’ve each come to a tentative secession agreement with the RSU.

Lamoine and Hancock last week joined Ellsworth in sending their withdrawal plans to the Department of Education in Augusta, where Commissioner Stephen Bowen will consider them for conditional approval. Ellsworth recently received approval for its plan earlier this week.

After the agreements are approved, each town will hold a public forum on the withdrawal effort before an eventual referendum.

At a meeting Tuesday with members from each town’s withdrawal committee, the three groups considered what might come next, including the possibility of banding together as an Alternative Organizational Structure.

An AOS — such as the one that manages the school districts on Mount Desert Island, outlying islands and Trenton — would retain the autonomy of each town keeping its own school board and maintaining its own budget while banding together to hire a superintendent and running a central administrative office.

While representatives from each community recognized that they were not in a position to create an AOS — school board representatives would have to make that decision after the potentially successful withdrawal — they said it was important to start having those conversations now. That way, when trying to convince residents to vote for withdrawal, supporters can present possible futures.

“We need to keep the dialogue going along these lines, because we need to communicate that we’re committed to reducing cost as much as possible, and that might mean an AOS,” said John Moore, an Ellsworth city councilor.

An AOS would provide one way for the three towns to keep costs down after leaving the RSU. While Ellsworth’s withdrawal committee is confident it can run an independent school district for less than it paid into the RSU, the other, smaller towns are less certain.

“Hancock is not going to pay for a superintendent on its own,” said Audrey Fogg, a member of Hancock’s withdrawal committee.

Still, an AOS is not the only option. The three towns could contract a superintendent together, the same way they did when they were members of School Union 92 before consolidation.

Under that administration, the towns joined together to pay a superintendent who responded to each town individually. Students from Hancock and Lamoine had the option to attend Ellsworth’s high school, but could also choose to attend Mount Desert Island High School or Sumner Memorial High School in Sullivan.

According to the proposed agreement with the RSU, Hancock and Lamoine would retain school choice as they have in the four years since the RSU was formed.

Regardless of the myriad possible future scenarios, each town is now focused on shifting its role from one of negotiating with the RSU to canvassing voters in an effort to drum up support for withdrawal.

Mark Rosborough, chairman of Ellsworth’s withdrawal committee, said that will mean presenting a concise, reasoned argument for leaving the RSU. Many voters, he said, will wonder about what the future would look like, but Rosborough said the argument is simple.

“How will Ellsworth interact with Hancock and Lamoine? Well, we did it for years. Why not just go back to how it was done before?” he said.

While the three towns originally hoped to hold the required public forums early enough for a June election, Ellsworth and Lamoine are now pushing for a November referendum on withdrawal. They say that will give them the time they need to campaign.

Hancock’s representatives were still considering a June election. Gary Hunt, chairman of that town’s withdrawal committee, said he was skeptical that a November election would leave enough time to elect a school board, hire a superintendent and pass a budget in time for the 2014-2015 school year.

The other towns cautioned that a special election in June just may not be possible, given that the Department of Education may require changes to the proposed agreement. Legislation regulating withdrawal sets a strict timetable for each step of the process, and they said the window may be too small.

“This all has to go like clockwork, and we’re working with a sundial,” said Doug Steward of Lamoine.